A centrifugal spinning device used for nanofiber/microfiber production

ABSTRACT

The present invention relates to a centrifugal spinning device, which is suitable for industrial production by being connected to high flow-rate polymer solution tanks or an extruder used for nonwoven nano/microfiber production, and which essentially comprises at least one rotary cylindrical spinneret through which the polymer material is injected for fabrication of nonwoven articles, at least two bearings located on both ends of the spinneret which enable it to be fixed on the system and rotate around a specific orbit, at least one motor connection member located on at least one end of the spinneret which provides the connection to the power supply that enables the rotational movement, at least one spinning die located inside the spinneret which enables the polymer materials to be homogenously distributed within the spinneret by means of its sectional area that is in the form of a half die.

FIELD OF THE INVENTION

The present invention relates to a centrifugal spinning device which is made suitable for industrial production by being connected to high flow-rate polymer solution tanks/pipe, melt extruder/pipe used for production of nonwoven nano/microfiber production.

BACKGROUND OF THE INVENTION

The nonwoven articles produced today are comprised of randomly aligned fibers which are 200 nanometer to 20 micrometer thick in the broadest sense. The current nonwoven production methods include meltblowing, solution blowing, spunbonding, air laying, wet laying and electrospinning. In centrifugal spinning system, polymer melt or solution is attenuated under centrifugal forces and brought to fiber form. Although there are different studies on centrifugal spinning, there is no design of an industrial-scale system for obtaining a highly homogenous nonwoven surface with a large width (over 20 cm).

A patent document related to centrifugal spinning discloses about use of the centrifugal forces in spinning of yarn rather than polymer. The said document is based on polymer melt or solutions being scattered under centrifuge and spun in the form of fiber and production of 2D technical fabric.

Another patent document in the state of the art discloses about polymer centrifugal spinning for thin fiber production from formaldehyde resins. Feeding polymer solution into an open cup and use of perforated cylinders are disclosed in the said document.

In another patent document in the state of the art, when a proper feeding cannot be performed, polymer materials get clogged in the perforated cylinder and when injected afterwards, problematic points occur. In order to prevent this, hard and blade-form obstacles are connected to the holes and thus accumulation of polymer is prevented by cutting the polymer flow in the centrifuge.

In another patent document wherein production of cellulose acetate and PEO polymers as a mixture via centrifugal spinning is disclosed, the microfibers leaving the centrifuge are delivered to the conveyor in a tube via air. It is also disclosed that fiber spinning continues in the tube wherein spinning is performed by air and that attenuation takes place.

In another patent document, obtaining thicker fibers in use of only centrifuge is criticized. Air flow with a velocity of 50-500 m/s accompanied centrifuge. Centrifuge rotor speed is in the range of 1000-11000 rpm. Although it is foreseen that presence of an additional aerodynamic system increases production costs, diameter of the fibers produced this way are in the range of 0.1-4 μm.

Centrifugal spinning system is used for spinning many polymers except the chain polymer materials. In a study conducted by BASF group, precondensed amine based chemicals having viscosity of 50-200 Pas are spun in the form of fibers. When the solution viscosity was high, the fibers stuck to each other, and when it was low, fragile and short fibers were obtained. Auxiliary chemicals can be used to reduce viscosity in this type of thermoset polymers.

On the other hand, DuPont company, which has developed Tyvek fabrics and flash spinning method, adds chemicals called spinning agents (whose evaporation temperature is below polymer melting temperature) to the polymer solution in a patent document they have filed. With the spinning agent, the jet speed increases up to 150 m/s and this reduces diameter of the fiber. The system is advantageous in terms of the product but the said spinning agent is the financially problematic part of it.

In another patent document in the state of the art belonging to DuPont, fibers having diameters below 1000 mm are obtained by feeding polymer melt onto a disk rotating at high speed. In the said system, the solid polymer is heated until it melts and when it melts it is fed to the rotary disk. This is an obstacle for mass production.

A further patent document in the art discloses about production of C nanofiber and nanotubes via centrifugal spinning system. The core-shell particles in the invention of the said document are centrifugally molten and made into fibers. It is asserted that high thermal SiC fibers can be produced by using Si—C precursor chemicals.

X. Zhang et al. have produced polyacrylonitrile nanofibers, which are used as reinforcing fibers in composites and as electrodes in batteries, from solutions via centrifugal spinning method, and have examined effective parameters (spinneret geometry, rotary disk speed, spinneret-collector distance, solution concentration).¹ ¹Y. Lu, Y. Li, S. Zhv.oang , G. Xu, K. Fu, H. Lee, and X. Zhang, <<Parameter study and characterization for polyacrylonitrile nanofibers fabricated via centrifugal spinning process ≦≦, Eur. Polym. J., 49, no. 12, pages 3834-3845, 2013

In order to examine the relation between the fiber morphology and rotary disk speed, they have produced nanofibers at different speeds with 13% by weight of PAN solution. It was observed that average fiber diameters decreased to 663, 541, 449 nanometers respectively for speeds of 2000, 3000, 4000 rpm. While the surface tension in a unit volume in the solution remained the same, centrifugal force increased. Thus, the nanofiber diameters decreased as the speed increased. In order to examine the effect of spinneret geometry, they have produced nanofibers at three different levels having diameters of 0.4 mm, 0.8 mm and 1 mm from 14% PAN solution at 10 cm collector-spinneret distance at a speed of 4000 rpm. As the spinneret diameter decreased, nanofiber diameter decreased as 895, 807, 665 nanometers. As the spinneret diameter decreased, feeding amount decreased. Consequently fiber diameters also decreased. The team who carried out production by setting the spinneret-collector distance as 10-20-30 cm has not observed any considerable change in the nanofiber diameters. The average fiber diameters were calculated as 665, 658 and 647 nanometers respectively for 10, 20 and 30 cm distances. Increase in the spinneret-collector distance may allow decrease in nanofiber diameters; however the actual importance of the spinneret-collector distance is determining the minimum distance to which the solvent in the solution can be removed. 10% concentration in which nanofiber production can be made was determined as the critical value for the solution. A continuous nanofiber production could not be carried out at concentrations below this value. The reason for this is that there is no sufficient chain complexity. Although viscosity and surface tension increased as the concentration increased above the critical value, continuous nanofiber was obtained. However fiber diameters also increased.

J. Ellision et al. have made researches on production of polybutylene teraphtlate polymer from melt via centrifugal spinning method. They have produced nanofibers by melting PBT which has high thermal and chemical stability. Increasing the rotary disk speed for the same temperature value did not cause a significant change on the fiber diameter. However, when the temperature increased at the same speed value, diameters of the fibers decreased.² ²K. Shanmuganathan, Y. Fang, D. Y. Chou, S. Sparks, J. Hibbert, and C. J. Ellison, <<Solventless High Throughput Manufacturing of Poly(butylene terephthalate) Nanofibers≦≦ACS Macro Lett., vol 1, no 8, pages 960-964, Aug. 2012

N. E. Zendar, used both melted and dissolved polycaprolactan polymer to feed into a centrifugal spinning device. As the temperature of the melt increased up to 200° C. in the production, viscosity and fiber diameter decreased. However, when the temperature rose above 200° C., although viscosity value decreased, diameters of the fibers increased and at the same time diameter distribution range also increased. The collector-spinneret distance was tried at three distances namely 10, 12, 14 cm, and no change was observed in the fiber diameters. However, differences were observed in the morphology of the fibers due to the cooling speed. It was determined that the fibers were broken and bent at shorter distances. As a result of the study conducted to determine the optimum speed by changing the rotary disk speed between 6000 and 18000 rpm, fiber production did not take place below a speed of 8000 rpm. At the speed of 8000 rpm, a few discontinuous fiber productions were observed. At the speed of 14000 rpm, homogenous and high quality fibers were obtained. When the speed was increased to 18000 rpm, droplets were formed due to rapid cooling.'³ N. E. Zander, <<Formation of melt and solution spun polycaprolactone fibers by centrifugal spinning≦≦, J. Appl. Polym. Sci., 2014.

K. Parker et al. produced nanofiber with polymer solutions containing different concentrations of PLA for biomedical applications. Continuous fibers could be produced with solutions having 8% and 10% by weight of PLA. It was observed that diameters of the fibers were larger in the production carried out with the 10% solution. For both ratios, increasing the speed of the rotary disk decreased the fiber diameter. In the production carried out with the 6% solution, droplets were observed together with the fibers. Upon further decreasing the concentration, with the 4% solution, only droplets accumulated in the collector. ⁴ ⁴M. R. Badrossamay, H. A. McIlwee, J. A. Goss, and K. K. Parker, <<Nanofiber assembly by rotary jet-spinning≦≦, Nano Lett., vol 10, no 6, pages 2257-2261, 2010.

In the current patents and publications, nanofibers having nano-scale diameters were produced. However the suggested systems are not suitable for mass production due to their flaws in terms of feeding problem, fiber collection system, etc. The problem of failing to collect the spun fibers homogeneously is encountered. Proper fiber diameter distribution curves could not be achieved. In the said studies, advantages of using the technique of centrifuge from melt together with an extrusion system suitable for mass production are not discovered.

PROBLEMS SOLVED BY THE INVENTION

The objective of the present invention is to provide a centrifugal spinning device used in production of polymer nanofiber/microfiber nonwoven production.

Another objective of the present invention is to provide a centrifugal spinning device which works in coordination with the solution mixer and the pump in the case that the polymer raw material is in solution form.

A further objective of the present invention is to provide a centrifugal spinning device which works in coordination with the molten polymer feeder (either a pipe/extruder) in the case that the polymer raw material is in melt form.

Another objective of the present invention is to provide a centrifugal spinning device wherein proper polymer melt and/or solution transmission is performed in the centrifuge cylinder by the design of a half die.

DETAILED DESCRIPTION OF THE INVENTION

A centrifugal spinning device used in nanofiber/microfiber production developed to fulfill the objectives of the present invention is illustrated in the accompanying figures, in which:

FIG. 1 is a side sectional view of the spinning device of the present invention.

FIG. 2 is a side sectional view of the application of the spinning die provided in the spinning device of the present invention in half fishtail/coathanger form.

FIG. 3 is a perspective view of the application of the spinning die provided in the spinning device of the present invention in half fishtail/coathanger form.

FIG. 4 is a perspective view of the rotary slotted spinneret used in one embodiment of the invention.

FIG. 5 is a perspective view of the rotary perforated spinneret used in another embodiment of the invention.

FIG. 6 is a general perspective view of the system wherein the spinning device of the invention is used and which enables fabrication of nonwoven articles.

The components in the figures are assigned reference numbers as follows:

-   -   1. Centrifugal spinning device     -   2. Spinneret     -   3. Hole     -   4. Slot     -   5. Bearing     -   6. Motor connection member     -   7. Spinning die     -   8. Inlet orifice     -   9. Flow channel     -   10. Flow section     -   11. Resistor     -   S. System     -   K. Conveyor     -   E. Extruder     -   M. Motor

The centrifugal spinning device (1) which is used in production of nanofibers for fabrication of nonwoven articles, essentially comprises

-   -   at least one rotary cylindrical spinneret (2) through which the         polymer material is injected for fabrication of nonwoven         articles,     -   at least two bearings (5) which are located on both ends of the         spinneret (2) and which enable it to be fixed on the system (S)         and rotate around a specific orbit,     -   at least one motor connection member (6) which is located on at         least one end of the spinneret (2) and which provides the         connection to the power supply that enables the rotational         movement,     -   at least one spinning die (7) which is located inside the         spinneret (2), and which enables the polymer materials to be         homogenously distributed within the spinneret (2) by means of         its sectional area that is in the form of a half die,     -   at least one inlet orifice (8), which is located on at least one         end of the spinning die (7), and through which the polymer         material is fed into the spinning die (7),     -   at least one flow channel (9) which extends from the end of the         inlet orifice (8) and enables transmission of the polymer         material along the spinning die (7),     -   at least one flow section (10) which is located at the outer         part of the flow channel (9) and in which the polymer material         is distributed homogenously between the spinning die (7) and the         spinneret (2),     -   at least one resistor (11) which enables to maintain the         temperature and consistency of the polymer material in the         spinning die (7).

The spinning device (1) of the present invention is used in the systems (S) which are operated for fabrication of nonwoven textile products.

In one embodiment of the invention, the spinneret (2) is in the form of a perforated cylinder and comprises holes (3) thereon (FIG. 5). The polymer material is injected through the said holes (3) and transferred onto the conveyor (K) in the form of filaments (fibers). The holes (3) can be circular as well as in other geometric shapes such as a triangle, trilobate, square, etc. Thus fibers having different sectional areas can be obtained.

In another embodiment of the invention, the spinneret (2) is in a helical form and comprises slots (4) thereon (FIG. 4). In this embodiment of the invention, the polymer materials are spun from each point of these slots (4) and are collected on a conveyor (K) to fabricate the nonwoven article.

The bearing (5) connects the spinneret (2) to the system (1) from both sides thereof and prevents the spinneret (2), which is under the effect of centrifuge, from oscillating out of its orbit.

The spinning die (7) enables the polymer material to be distributed homogenously from the flow channel (9) towards the flow section (10) and then to flow equally through the holes (3) or the slots (4) on the spinneret (2) by means of its geometry which is symmetrically half of the fishtail type, coat-hanger type or T-type dies. The fibers flowing from the spinneret (2) are collected on the conveyor (K) under the influence of centrifuge. The fibers collected on the conveyor (K) form the two dimensional textile product form. In the preferred embodiment of the invention, the spinning die (7) has a three sided cross-sectional area (FIG. 2 and FIG. 3).

In one embodiment of the invention, the polymer material is in melt form and it is fed into the spinning die (7) through the inlet orifice (8) by means of an extruder (E) or any other means for molten polymer transfer. In another embodiment of the invention, the polymer material is a solution and this polymer solution is fed into the spinning die (7) through the inlet orifice (8) preferably by means of pump and pipes.

In the spinning device (1) of the present invention, from one end of the spinneret (2) polymer material is fed via an extruder (E) or a pump, while at the other end thereof a motor (M) was provided which enables the rotational movement of the device (1). Larger drive forces are generated by using high-speed motors (M) and thus smaller fiber diameters can be achieved. In one embodiment of the invention, the device (1) is driven by a motor (M) reaching a speed of 40000 rpm.

The resistor (11) is mounted on or within the spinning die (7) in order to provide temperature control. In one embodiment of the invention, the resistor (11) is a cartridge-type located towards inside of the spinning die (7) and it is supported by a thermocouple for measurement of the temperature value.

Thanks to the coordinated use of the spinning die (7) and the resistor (11) provided in the spinning device (1) of the present invention, consistency of the polymer material can be adjusted as desired and homogenous distribution of the polymer material within the spinneret (2) can be ensured. 

1. A centrifugal spinning device (1) which is used in production of nano and/or micro fibers for fabrication of nonwoven articles, comprising: at least one rotary cylindrical spinneret (2) through which the polymer material is injected for fabrication of nonwoven articles; at least two bearings (5) which are located on both ends of the spinneret (2) and which enable it to be fixed on the system (S) and rotate around a specific orbit; at least one motor connection member (6) which is located on at least one end of the spinneret (2) and which provides the connection to the power supply that enables the rotational movement; at least one spinning die (7) which is located inside the spinneret (2), and which enables the polymer materials to be homogenously distributed within the spinneret (2) by means of its sectional area that is in the form of a half die; at least one inlet orifice (8), which is located on at least one end of the spinning die (7), and through which the polymer material is fed into the spinning die (7); at least one flow channel (9) which extends from the end of the inlet orifice (8) and enables transmission of the polymer material along the spinning die (7); at least one flow section (10) which is located at the outer part of the flow channel (9) and in which the polymer material is distributed homogenously between the spinning die (7) and the spinneret (2); and at least one resistor (11) which enables to maintain the temperature and consistency of the polymer material in the spinning die (7).
 2. A centrifugal spinning device (1) according to claim 1, wherein the spinneret (2) is in the form of a perforated cylinder and comprises holes (3) thereon.
 3. A centrifugal spinning device (1) according to claim 1, wherein the spinneret (2) has a helical form and comprises slots (4) thereon.
 4. A centrifugal spinning device (1) according to claim 1, wherein the bearing (5) connects the spinneret (2) to the system (1) from both sides thereof and prevents the spinneret (2), which is under the effect of centrifuge, from oscillating out of its orbit.
 5. A centrifugal spinning device (1) according to claim 2, wherein the spinning die (7), by means of its geometry which is symmetrically half of one of a fishtail type, a coat-hanger type and a T-type die, enables the polymer material to be distributed homogenously from the flow channel (9) towards the flow section (10) and to flow equally through the holes (3) or the slots (4) on the spinneret (2) and thereby to fabricate a textile product on the conveyor (K).
 6. A centrifugal spinning device (1) according to claim 1, wherein the inlet orifice (8) enables the polymer material that is in melt form to be fed into the spinning die (7) by means of an extruder (E).
 7. A centrifugal spinning device (1) according to claim 1, wherein the inlet orifice (8) enables the polymer material that is in solution form to be fed into the spinning die (7) by means of a pump.
 8. A centrifugal spinning device (1) according to claim 6, wherein through one end of the spinneret (2), polymer material is fed via the extruder (E) or a pump, while at the other end, there is provided a motor (M) which enables the rotational movement.
 9. A centrifugal spinning device (1) according to claim 1, wherein the cartridge-type resistor (11) is mounted on or within the spinning die (7) in order to provide temperature control.
 10. A centrifugal spinning device (9) according to claim 1, wherein the resistor (11) is supported by a thermocouple for measurement of the temperature value.
 11. A centrifugal spinning device (1) according to claim 3, wherein the spinning die (7), by means of its geometry which is symmetrically half of one of a fishtail type, a coat-hanger type or a T-type die, enables the polymer material to be distributed homogenously from the flow channel (9) towards the flow section (10) and to flow equally through the holes (3) or the slots (4) on the spinneret (2) and thereby fabricate a textile product on the conveyor (K).
 12. A centrifugal spinning device (1) according to claim 7, wherein through one end of the spinneret (2), polymer material is fed via an extruder (E) or a pump, while at the other end, there is provided a motor (M) which enables the rotational movement. 